We propose to generate a computer-based model of the development of the C. elegans egg-laying system using state chart-based modeling. The nematode C. elegans is one of the best-defined multicellular animals in existence- anatomically, genetically and molecularly. It is a powerful model system for many fundamental biological processes. The egg-laying system of C. elegans hermaphrodites has been intensively studied in the last two decades, helping to elucidate the development of its four major components as well as the interactions between them. These components include the gonad, the vulva, the egg-laying muscles, and the HSN neurons. The visual formalism of statecharts, within the general framework of "object-oriented modeling" is a modeling language that is both legible to biologists as well as computer scientists and faithful to the logic of biological systems. Therefore, we will employ this methodology to to model the egg-laying system. Statechart-based formal modeling methods were originally developed by members of our collaboration for the field of system design. As a small-scale biological application of these methods was recently applied to T cell activation. This model served as a feasibility test and integrated phenomena associated with cell-cycle control, signal transduction, cell fate, cell behavior and location. We now propose to extend this to more complex biological phenomena, that will incorporate additional aspects of development including cell fate acquisition, cell migration, axon guidance, and apoptosis. In principle, our model will handle virtually all aspects of development, ultimately allowing our results to be extended to and used by the entire C. elegans community and to other systems as well. By this approach, we hope to pave the way to modeling larger biological events to eventually describe such complex phenomena as the development of all of C. elegans and aspects of human biology and disease progression.